This application claims the priority of German application 196 35 867.1, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an arrangement for actuating the shift mechanism of a change-speed gearbox and for engaging and disengaging a main clutch arranged upstream of the change-speed gearbox in the flow of force. In particular, an auxiliary mechanism transforms a rotary motion of a mechanism input member into a reciprocating motion of a mechanism output member allocated to the main clutch, and an auxiliary mechanism transforms a rotary motion of a mechanism input member into a reciprocating motion of a mechanism output member allocated to the shift mechanism. A device drives the mechanism input members of the two auxiliary mechanisms by a common servomotor, and a device couples and uncouples the mechanism output member allocated to the shift mechanism with regard to its drive connection relative to the device for driving the mechanism input members.
In an earlier arrangement of the foregoing type known to the applicants, an electric motor is in drive connection. with the worm of a worm gear unit. The worm wheel is arranged in a Notionally fixed manner relative to the two mechanism input members used in the form of one eccentric each. The one eccentric interacts with a clutch disengaging lever of the main clutch and the other eccentric interacts with a fork-shaped link on the one lever arm of a differential lever. The other lever arm has a toothed segment which engages in a rack profile of a shift rod of the shift mechanism.
Consequently, the clutch disengaging lever and the shift rod are in such a fixed kinematic allocation to one another that, during a gear shift, the main clutch is first always completely disengaged, then the instantaneous gear is disengaged, subsequently the shift lane of the new gear is selected (with a separate selecting device), then in further sequence the new gear is engaged, and finally the main clutch is re-engaged. This sequential progression of the actuations of the main clutch and shift mechanism leads in each case to a long shift time during the gear shifts.
DE 43 36 446 A1 discloses an arrangement for actuating a main clutch to be provided in the flow of force between a drive motor and a change-speed gearbox. An electric motor is connected by a worm gear unit to an eccentric disc of an auxiliary mechanism for transforming a rotary motion into a reciprocating motion and the output member of the latter acts on the main clutch. The eccentric disc is also coupled to a spring-energy accumulator for assisting the clutch actuation.
EP 0 527 389 A1 discloses a further arrangement for shifting a two-stage axle drive of a utility vehicle. A spring-energy accumulator, as a function of the position of a device (e.g., a clutch) controls the flow of force of the drive torque to the drive axle and can be connected in the shift-force transmission between the shift mechanism at the axle drive and an electric shift motor. Thereby, the shift is carried out only when the flow of force to the drive axle is interrupted. The electric motor acts on a worm gear unit, the worm wheel of which has an eccentric which engages in a slotted-link guide of the input member of the spring-energy accumulator for transforming a rotary motion into a reciprocating motion.
An object of the present invention is to shorten the shift time in such an arrangement. This object is advantageously achieved according to the invention by providing that the two mechanism input members are connected to one another by an auxiliary clutch used as the device for coupling and uncoupling the mechanism output member allocated to the shift mechanism, and in that the auxiliary clutch, irrespective of the position of the mechanism output member allocated to the main clutch, can be engaged and disengaged by a clutch final control element derivable by a servomotor.
In one embodiment of the arrangement according to the present invention, the basic configuration of the mechanical change-speed gearbox is not altered, but all shift and control elements can be adaptively arranged at the periphery of the surrounding zone of the gearbox. The shift times can be markedly reduced by activating the control functions at the same time or at overlapping times (declutching and shifting as parallel function steps). By the use of only one actuator and a few control elements, the overall complexity and thus the costs can be kept down without functional disadvantages having to be tolerated.
In automated change-speed gearboxes, the problem may arise that, due to shifts always being associated with an interruption in tractive force on account of the gearbox design, a lack of comfort as a result of the occurrence of vehicle longitudinal vibrations may be felt in certain operating states (e.g. accelerating actions) due to the interruption of the drive moment. In the arrangement according to the present invention, therefore, it is of particular advantage that critical shift manoeuvres take place in a short time sequence. Declutching and shifting into neutral can be carried out at the same time in order to achieve the desired shift-time gain, in which case electronic engine management may be incorporated in the control.
However operating states, e.g. driving downhill, also occur in which a sequential progression of the actuations of main clutch and shift mechanism is necessary from the functional point of view. In this respect, too, the arrangement according to the present invention provides the precondition for variable use of the individual functions in the control of the gear shift.
In the arrangement according to the invention, a worm gear unit can be driven via an actuator (servomotor in electromechanical or hydraulic basic configuration). The worm gear unit activates, via an eccentric, the engagement and disengagement of the main clutch and, in sequence therewith or parallel thereto, the shifting and selecting action. Unlike a prior arrangement known to applicants, the shifting and selecting function in the arrangement according to the present invention can be initiated via a frictional or positive auxiliary clutch, which can be engaged and disengaged by a clutch final control element driven by a servomotor, such that an optimum operating sequence results. All basic functions performed here may be realized in a modular type of construction, including an electronic control unit for the shift sequence.
In the arrangement according to the present invention, the shifting and selecting operations may be carried out in a manner previously described in U.S. patent application Ser. No. 08/818,358, filed Mar. 17, 1997 or according to German Application Serial No. 196 35 866.3-14. The relevant function units may likewise be accommodated in the drive module.